One of the foundations of any ecosystem is the hidden invisible universe so to speak that operates under the ground and I've already written about this in a piece about the Earth's Biological Soil Crusts. - see Footnote - To term these soil components as nothing more than primitive organisms is an insult to the biological mechanically running world. That would be like comparing a powerful brilliantly engineered expensive Rolls Royce engine to it's Cooling System Hose and insisting the Engine is far more important than the lowly hose. Yet that Rolls Royce engine would be nothing without the Cooling System Hose. Take a quick view of this short Video which was recently recorded on the Bio-Crust Site called:
Jim Sears, TerraDerm
|Illustration from Dawson's Lab|
As the Acacias, Mesquite, Paloverde, Ironwood trees, etc reach maturity, then the mechanisms of Hydraulic descent can ALSO kick in and take over sucking as much surface soil water as possible after rainfall and pumping it deep into the earth to later be utilized through Hydraulic lift and redistribution as needed. If there are times of heavy seasonal rainfalls, then such mechanisms may even restore a measure of Aquifir water table levels previously lost (Human Agricultural Activities), raising those levels to better serve the environment and even humankind if they are able to utilize such resources responsibly. This is the healthy process that should be your goal in any productive restoration project.
Most of my focus has been on Mesquite Dune projects and specific desert environs where soils don't necessarily have a lot of obstacles such as bedrock or hard pan barriers. So most illustrations I've given are perfect in their ideal appeal to taproot development, but not all geology is the same. For example my mum's property has very deep sandy loam soil whose origins come off a rather large mountain over a period of 1000s of years into an alluvial fan. That's why her California Sycamores have done so well. I knew this ahead of time and trained these 1 gallon trees into the deeply rooted 30+ foot high 6 year old trees they are today. Knowing soil dynamics and structural makeup truly helps. Not everything considered to be deeply taprooting trees or shrubs will respond favourably the same way. But there are possibilities and other viable options. Recently info has come out though that illustrates that even in tough soils with taproot engineering goals, such obstacles as clay and bedrock can be over come by the plant. See:
|Source: Soil Types and Structures Module DEPI, Victoria|
Sometimes depending on soil geology they may fail or simply take longer finding those open soil fractures to drive deeper. Take this illustration here to the left. It animates what is called Hard Pan which is a dense compact layer of soil which is almost like condense compacted concrete or rammed Earth for which water movement and even root penetration is almost ZERO. Water drainage is a big problem. The illustration shows where drilling or some other break through may be necessary to create a favourable change to this type of soil dynamics. This is exactly the kind of soil problems found around San Diego areas on the Mesas like Kearny Mesa, Miramar and Sierra Mesa where hard pan is common. These communities are basically all on the same table lands and have almost identical sub-soil issues. It is some of these features which allow for Vernal Pool development in nature to work. We (the Property Management Co I worked for) had an apartment complex where we needed to make some underground plumbing system changes. The hard pan was just below the surface at about 5 foot deep with the hard pan itself being a foot to foot and a half thick. It literally is as tough as concrete and the porosity just as bad. We had to use Jack Hammer and to punch holes through and once opened up a backhoe took care of the rest. Soil below that is well draining. Prior to Human building of the area, native vegetation for the most part was never trees, just low Coastal Chaparral scrub.
|There are three levels to this soil profile|
The top & bottom are porous soils
The middle is hardpan soil. It may be
necessary to mechanical breakthrough to
facilitate rapid taproot development.
I know of one such property in the Spring Crest area of Santa Rosa Mountains above Palm Springs CA. The underlying ground material was hard granite bedrock. It didn't perc well. Negative Perc-Test, no House Building Permits. Solution often used there were to drill numerous deep narrow holes over a given area and load these holes with just explosive charge enough to fracture the granite bedrock underneath to allow water percolation. But hey, that may be an option for some Habitat improvement. Thereafter trees roots and proper microbiological material properly injected into the earth should take over from there.
The above link has a great article on root structure couple with microbial interactions and climate change.
|photo Pinal County Arizona|
Plant Root Spiraling Mechanisms: Ability to Bore Through Earth's Toughest Soil Structure
|image: Colorado Guy|
Seriously, even here on the top of the Peak with less than ideal soil. No Sandy alluvial flood plains here. What some plants are able to accomplish is amazing.
|photo - Gene Breker|
Another beautiful illustration of the spiraling drilling mechanism of a taproot comes from a company which sells Tillage Radish seed to farmers as a cover crop which not only opens up deep layers of subsoils, but also acts as a cover crop to prevent weeds before planting corn next season. But lets focus on the spiraled twisting nature which is also found in the top growth of any plants. One has to wonder if a measure of water is injected into the ground by the Mesquite or Acacia tree taproots ahead of the root cap to facilitate opening of tight soil particles. So Hydraulic descent may even start very early in the plants life rather than later. One can only imagine and speculate since in most desert ecosystems, rainfall is often less than 3 inches. Germination takes place, seed drives spiraling root shaft quickly into a foot or so of moist soil layers from present rainy season at best, then power drills through nothing but dry layers of Earth's subsoils thereafter before hitting the actual water table below. Once again science has discovered and illustrated the mechanism by which such amazing engineering feats in nature are possible. But do you have the insight to replicate such engineering into your landscape or Habitat Restoration blueprint ?
|Image - Tarleton State University|
Okay let's shift some gears here- Tamarisks, I don't want to spend much time on this one as I have a post dealing with Tamarisk Trees. There are good and bad points on many living things, in this case not the plant, but the Human Idiocy Factor. There are incredible opportunities for more responsible construction of desert windbreaks utilizing local resources at very little cost. Here is the link:
Trees, and even more specifically forests, have been shown to be critical for regulating climate and creating cooler microclimates, for building soils and therefore the water retentive capacity of the land (acting like a giant sponge that releases water slowly), for reducing erosion and its resultant siltation of waterways, for reducing salination, for creating wildlife corridors, for acting as windbreaks, for supplying humanity with both timber and non-timber products, for cleansing water and for creating the air that we breathe.
Start Getting A Clue. The Earth has very little time left !!!
References on Soil Crusts: